54 
in  some  other  way  deliberately  bleed  them  to  deaths  they  still  tap 
them  with  an  utter  disregard  of  all  precautions  for  their  preserva- 
tion. Such  methods  are  out  of  the  question  when  we  come  to  tap 
the  trees  on  the  rubber  plantation.  Here  absolutely  the  first  con- 
sideration is  not  only  to  conduct  the  tapping  in  such  a way  as  to 
preserve  the  life  of  the  tree  but  even  to  prevent  this  operation  from 
injuring  its  vigour  and  growth. 
It  does  not  require  much  demonstration  to  show  that  the  process 
of  tapping  must  to  a considerable  extent  depend  upon  the  position, 
distribution  and  arrangement  of  the  laticiferous  vessels  in  the  trees. 
It  is  generally  stated  that  the  milk-ducts  of  rubber  trees  lie  in  the 
layer  of  bast  underneath  the  bark,  and  that  no  milk-ducts  are  to  be 
found  in  the  inner  parts  of  the  trees,  the  wood  or  cambium.  This, 
as  a general  statement  may  be  true  enough,  but  it  certainly  does 
not  strictly  ap|)ly  in  the  case  of  Castilloa  elastica.  If  we  chop  one 
of  the  stout  branches  off  a Castilloa  tree,  or,  better  still,  if  we  cut 
‘ down  a young  tree,  and  carefully  examine  the  cut,  we  can  easily  see 
with  the  naked  eye  that  although  the  bulk  of  the  exuding  latex 
issues  from  the  layer  of  bast  immediately  beneath  the  bark,  still 
there  are  - quite  a number  of  apparently  rather  large  milk-ducts 
distributed  through  the  wood  of  the  tree^  and  also  that  there  is  a 
considerable  exudation  in  the  lignified  tissue  surrounding  the  pith 
centre  of  the  trees.  It  will  be  a highly  interesting  problem  to  as- 
certain' by  a carefully  microscopic  study  of  the  various  strata  of  the 
trunk  of  the  Castilloa  tree^  whether  there  is  any  direct  communica- 
tion (anastomose)  between  these  widely  separated  milk-ducts  in 
the  various  parts  of  the  tree.  How  far  similar  conditions  exist  in 
other  rubber  trees,  I am  at  present  unable  to  say,  but  it  seems  to 
me  very  improbable  that  Castilloa  stands  alone  in  this  respect. 
Whether  there  is  any  communication  between  the  milk-ducts  in 
the  different  parts  of  the  tissues  of  the  trunk  of  Castilloa  or  not, 
can  however,  not  alter  the  fact  that  in  tapping  the  trees  on  a rub- 
ber plantation  only  those  layers  of  the  trunk  situated  on  its  peri- 
phery can  be  drawn  upon.  Indeed_,  it  is  the  layer  of  bast  only 
immediately  underlying  the  bark  which  is  worth  considering  for 
tapping  purposes,  as  it  is  generally  admitted  that  any  cuts  into  the 
wood  of  the  tree  are  liable  to  permanently  injure,  or  even  altogether 
destroy  it.  It  is  therefore  quite  clear  that  as  regards  the  rubber 
plantation  entrusted  to  me,  one  of  the  most  important  questions  to 
be  solved  was  to  ascertain  and  decide  upon  the  most  satisfactory 
method  of  tapping  the  trees. 
A microscopic  examination  of  longitudinal  sections  of  the  bast 
layer  of  Castilloa  at  once  revealed  the  fact  that  while  this  layer 
contains  an  enormous  number  of  milk-ducts  running  longitudinally 
through  the  tissue^  there  are  surprisingly  little  evidence  of  lateral 
intercommunication  (anastomoses)  between  them.  In  exact  agree- 
ment with  this  observation  is  the  fact  that  longitudinal  incisions 
produced  an  absurdly  small  flow  of  latex,  indeed,  in  many  cases, 
none  at  all,  this  for  the  simple  reason  that  the  number  of  milk-ducts 
opened  by  a vertical  incision  is,  in  the  absence  of  horizontal  branch- 
ings, simply  the  number  of  milk-ducts  occupying  the  width  of  the 
